1. Field of the Invention
The invention relates to a method for the determination of the molecular weight and structure of organic compounds, synthetic or natural polymers, polynucleotides and polypeptides from their absorption spectra.
2. Description of the Prior Art
The absorption peaks or their shifts in visible or ultraviolet light can generally only rarely be used for the determination of chemical structure because they are irregular and unpredictable. Also the chemical substitutions in aliphatic chains or aromatic rings very often cause irregular shifts of absorption peaks and another approach to this problem is needed.
There is presently no simple general single method for polymer analysis. Several more or less complicated methods must be used in order to reveal the molecular weight and the composition of the studied polymer. For example, the nucleotide and/or amino acid analyzers are based on a complete nucleotide or peptide hydrolysis by strong acids or alkalis. This is laborious and causes many problems.
In one such analysis, during hydrolysis part of the carbohydrate from nucleotides or several amino acids from peptides (i.e. tryptophan, asparagine, glutamine and cysteine) are completely destroyed, while others (i.e. serine, threonine) are partially destroyed. The analysis of the remaining nucleic bases or amino acids in the hydrolysate is also accompanied by relatively large errors. Thus these results are not very reliable and reproducible. Additionally, a relatively large amount of the sample is needed and the analyzed sample is completely lost.
The additivity of chemical group contributions has been found with different physicochemical properties of organic compounds, for example, parachor, molecular refractivity, or optical rotation. This approach has not been applied to the uv or vis absorption spectral peaks in any great detail. The reason is obviously because the absorption peaks are broad, do not confine to a single wavelength, and extend over wide regions. In contrast to their spectra, the positions of the peaks of the absorbing chemical groups are not accurately predictable because of the unpredictable excited states.
Although several sets of empirical rules have been established (for example, Woodward's or Fieser's rules for the maxima or dienes or dienones), the maxima are generally only poorly related to the structure. Chain or aromatic ring substitutions create more or less irregular absorption shifts to longer or shorter wavelengths and tautomery invalidates most of the empirical rules. This is the main reason why the visible and ultraviolet absorption maxima can only rarely be used for the qualitative identification and/or quantitative determination of chemical structural characteristics.